Conventionally, an electronic apparatus that uses primary and secondary batteries as a power source has widely been used. The electronic apparatus of this type has a battery housing portion into which the primary battery or secondary battery is inserted. From the battery housed in the battery housing portion, a power is supplied to the apparatus and thereby the electronic apparatus is driven. By putting the secondary battery for use in the electronic apparatus in a dedicated battery charger, it can be re-charged and used repeatedly.
As the primary battery for use in an electronic apparatus that is driven by a battery, a size AA battery is available. Some electronic apparatuses that use the size AA battery have a battery housing portion into which two size AA batteries are inserted in consideration of power consumption of the apparatus or battery life.
In order to house the secondary battery in the battery housing portion in a compatible manner with the size AA battery in an electronic apparatus capable of using both primary and secondary batteries, a secondary battery having the same shape as that of the size AA battery is adopted. By making the shape of the secondary battery identical to the shape of the size AA battery as described above, it is possible to put the secondary battery in the battery housing portion for the size AA battery in a compatible manner with the size AA battery.
In this case, in the secondary battery which can be housed in the battery housing portion for the size AA battery in a compatible manner, when the battery housing portion into which two size AA batteries are inserted is used, the secondary batteries each having the same shape as that of the size AAA battery are arranged, as an assembled battery.
Some electronic apparatus capable of using both primary and secondary batteries are configured to use a DC adapter. The DC adapter converts a commercial alternating power into a DC power using an AC/DC converter and supplies the apparatus with the DC power. Some DC adapters of this type are configured to be housed in the battery housing portion for primary and secondary batteries. In order to realize this configuration, proposed is a DC adapter having substantially the same size as that of the assembled secondary battery whose size is the same as that obtained by arranging the two size AA batteries and having substantially a similar shape to the assembled secondary battery. Electrodes are formed on the DC adapter. The DC adapter is provided with electrodes. When being housed in the battery housing portion for the primary and secondary batteries, the electrodes come into contact with terminals formed in the battery housing portion with which the electrodes provided in the primary and secondary batteries come into contact. Therefore, when the DC adapter is housed in the battery housing portion, the electrodes come into contact with terminals formed in the battery housing portion, and a DC power is supplied to an electronic apparatus through the terminals and electrodes.
The use of thus configured DC adapter eliminates the need to form a DC jack connector for an AC/DC adapter or DC adapter on the electronic apparatus side, that is, it is only necessary to form a battery housing portion on the electronic apparatus side, contributing to reduction in the number of parts of the electronic apparatus to be used and, eventually, the size of the electronic apparatus itself.
In such a DC adapter that can be housed in the battery housing portion for the primary and secondary batteries in a compatible manner, electrode terminals formed on the DC adapter have defined polarity like the primary and secondary batteries. Thus, if the DC adapter is inserted into the battery housing portion with the polarity thereof wrongly set, the electronic apparatus does not operate, or any trouble related to the operation of the apparatus may be caused. In order to prevent the wrong insertion, a configuration can be considered in which the DC adapter is formed in a left-right asymmetrical shape and the shape of the battery housing portion is correspondingly formed. As a result, however, when the primary or secondary battery, or assembled battery obtained by arranging the secondary batteries are inserted into the battery housing portion having the above configuration, the inserted battery may rattle within the housing portion. In addition, assume that the terminals of the battery housing portion with which the electrodes of the DC adapter come into contact are shared between the primary or secondary battery and DC adapter. In this case, when the DC adapter is used in the apparatuses other than its conforming apparatus, there is a possibility that the operating voltage may differ from that of the primary or secondary battery, so that it is impossible to ensure safety of the electronic apparatus, in some cases.